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Thursday, 26 August 2010

Climate change has been resulting in quite a many detrimental manifestations which tend to have a domino effect: fluctuations in temperature and precipitation (resulting in climate variability), as well as extreme manifestations such as drought, storms, rise in sea levels, and frequent severe weather events.

Consider the research by Grinsted et al (2009) who used a ‘physically plausible four parameter linear response equation’ to relate nearly 2,000 years of global temperatures and sea level. Assuming that this relationship holds from 200 to 2100 AD, IPCC’s temperature scenarios and reconstructed past sea level scenarios were used to visualise future sea level scenarios. The result suggests that climate change will lead to a 0.9-1.3 m change in sea level between 2090-2099. This bodes a certain flooding of low lying coastal regions and islands. Island countries such as Maldives would practically cease to exist. Whilst countries such as Bangladesh may not face such obliteration, such a sea level rise would flood 1/3rd of the country, displacing millions of humans and severely affecting agriculture, irrigation, and livestock.

Climate change also has a perceptible impact on human morbidity and mortality (Patz et al, 2005). Climate fluctuations have been linked to diseases and ailments- the evident effects of heat/cold (which, for instance, follows a U-shaped dose-response function with increased mortality in the extreme heat and cold), traumatic physical and mental ailments, and even cardiovascular and respiratory illnesses. This even results in altered transmission of infectious diseases (for instance, changes in temperature has been associated with salmonellosis in Europe and cholera in the ‘American south-west’; whilst, changes in rainfall has been associated with Rift valley fever in East Africa, and Hantavirus pulmonary syndrome and cholera in the American south-west and Bangladesh). When one factors in the effects of climate change on air pollution and the greater ecosystem, the result is quite chaotic. If the future projections of climate change are plausible, then it is likely that these health risks may rise significantly. The ‘potentially vulnerable’ regions includes the temperate latitudes (which may warm disproportionately), and the regions in and around the Pacific and Indian oceans (substantial rainfall variability).

But even though the economic North/developed countries are responsible for most of the greenhouse gas emissions, the damaging effects of their actions are most perceived in the poor countries of the South which has (as of yet) contributed least towards the GHG emissions.

Thursday, 19 August 2010

The recent oil spill in the Gulf of Mexico released, as we have all seen on tv, a lot of oil. Quite how much is a "lot" is a bit of a guess, but roughly 4.9 million barrels, or 784 million litres*. What actually happened to this oil was reviewed recently in an article in Science (Kerr 2010). Only about 0.1% was recovered from beaches and marshes (that´s still an awful lot of oil!). About 17% was siphoned away at the well head, 5% burned off at the surface, and only 3% skimmed off by booms, despite a lot of effort and money spent. And the other 75%? It's, er, disappeared.

So where did this oil go? Some evaporated, but with luck most of it was eaten.

Oil is energy, that's why we use it in our cars and power stations. And energy means food. There are actually quite a few bacteria that digest and breakdown crude oil, and these are massively important in the recovery of the ocean from disasters like this. They work as a consortium, each concentrating on a particular fraction of the oil, and as one hydrocarbon is degraded to another, other bacteria take over. The first, and so in many ways the most important, are Alcanivorax species (Vila et al 2010). These are found in tiny quantities in unpolluted waters, but their numbers rocket when in the presence of linear and branched alkanes, common in crude oil. In fact they are so specialised for this type of hydrocarbon that without long chain alkenes they grow very poorly, but by then their job is done. Now other species such as Roseovarius and Marinobacter take over.

This breakdown was helped by the massive release of chemical dispersants at the oil head, 1.1 million gallons (Kintisch 2010). These are similar to the detergent in your kitchen, breaking down lumps of oil into tiny droplets, which are "dispersed" and can be attacked much more efficiently by bacteria. This was very controversial, as dispersants are pretty toxic and an immense quantity was involved. Still, it seemed to work, and much of the oil was broken down into 1-10 micrometer droplets. In fact, it started to raise fears that it was working TOO well, a microbial explosion depriving the ocean floor of oxygen and creating a huge dead zone. But this seems not to have happened, and in fact so far the prognosis is good.

Wednesday, 4 August 2010

Having highlighted a recent paper on the presence of Lead in game, I have decided to commence a series of specialised ‘limelights’ on the effects of Lead bullets/pellets in humans as a result of game hunting. However, before I address my assignment, I shall first provide a succinct background on Lead’s toxicity.

InceptionFor thousands of years, Lead has been widely extracted and used by mankind, mainly due to the availability of its many ores as well as its malleability. In fact, Lead used to be the second most used metal (after Iron).

A great danger of Lead toxicity is that the symptoms may lag physiological changes, i.e. the affected individual may remain unaware of the danger (similar to the effect of cholesterol). Lead in the blood does not excrete and a major proportion sequesters in soft tissues and bone from where it may be switched on especially during pregnancy (Tellez-Rojo et al, 2004) or old age (Schwartz and Stewart, 2007).

Over the past 50 years, as a result of new studies revealing the toxic effects of Lead at lower levels, the benchmark levels have declined (60 μg/dL in 1960; 25 μg/dL in 1985; and, 10 μg/dL in 1991) (Needleman, 2004). And although the current CDC benchmark level is 10 μg/dL, the published studies indicate that it would be inane to consider even a trifling level of Lead exposure as being harmless (Bellinger and Bellinger, 2006)- for instance, Lanphear et al (2005) has associated maximal blood Lead levels lower than 7.5 μg/dL with permanent cognitive damage and intellectual deficits in children, whilst Menke et al (2006) associated 2 µg/dL as having increased risk of cardiovascular mortality in adults.

Schwartz, B., & Stewart, W. (2007). Lead and cognitive function in adults: A questions and answers approach to a review of the evidence for cause, treatment, and prevention International Review of Psychiatry, 19 (6), 671-692 DOI: 10.1080/09540260701797936

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